Boats and other water-going vessels are often required to display a light on the highest part of the vessel. Because the highest point is usually the top of a mast which may support sails or radio antenna, for instance, it may be difficult to replace a failed lamp in that location. It, therefore, would be desirable to employ a lamp located at the base of the mast, where it is easily reached, and to direct the light to the top of the mast with a fiber-optic, or light, guide. However, the problem arises of how to distribute the light reaching the upper end of the light guide to meet a required beam pattern. The required pattern for at least one class of ships is to provide 94 candela for 360 degrees in a horizontal plane and which extends 71/2 degrees above and 71/2 degrees below the horizontal plane.